The transamination reaction between a Schiff base polypyrrolic macrocycle, H4Ltet/oct, where tet = tetramethyl (C38H36N8), oct = octamethyl (C42H44N8), and [UO2(THF)2{N(SiMe3)2}] results in the sole formation of mono uranyl complexes [UO2(THF)(H2Ltet)], 7, and [UO2(THF)(H2Loct)], 8. The molecular structure of 8 was confirmed by an X-ray diffraction study which shows that the macrocycle folds to form a Pac-man shape. The reaction between 7 and [M{N(SiMe3)2}2], where M = Mn, Fe, Co or Zn, results in the formation heterobimetallic complexes, [UO2(THF)M(THF)(Ltet)], 9, 10, 11, and 13, respectively. The structures of 9 and 11 have been confirmed by X-ray crystallography and show that there is a direct donor bond from one oxo ligand of the uranyl dication to the transition metal, and characterisation by vibrational spectroscopy suggests that the bonding of the uranyl dication has weakened. The double deprotonation of 8 with KN(SiMe2R)2, where R = Me, Ph, and subsequent salt elimination reaction with MX2, where M = Fe, X = I and M = Zn, X = I, Cl, results in the formation of the first discrete reductively functionalised pentavalent uranyl complexes [UO(OSiMe3)(THF)(FeI)2(Loct)], 17, [UO(OSiMe2Ph)(THF)(FeI)2(Loct)], 18, [UO(OSiMe3)(THF)(ZnI)2(Loct)], 19, and [UO(OSiMe3)(THF)(ZnCl)2(Loct)], 20, which contain a covalent Si–O bond to one oxo-group. Complexes 17 to 20 have been fully characterised and the solid state molecular structures of 17 and 19 were determined. Investigation into the mechanism of the functionalisation suggests that the intermediate complex [UO2(THF)(K2L)] is highly oxidising and reactive and promotes the single electron transfer reaction with trimethylsilyl reagents and results in the homolytic cleavage of bonds and concurrent reduction of the uranyl ion. The solution redox properties of 8 have been measured by cyclic voltammetry, and exhibits a single electron reduction at -1.17 V (vs. Fc/Fc+). The reaction of 8 with one equivalent of cobaltocene results in the formation of the pentavalent uranyl complex [CoCp2][UO2(THF)(H2Loct)], 26. The reaction of 8 with two or three equivalents of B(C6F5)3 results in the formation of [UO2(H2Loct)B(C6F5)3], 31, and [UO2(H2Loct)(B{C6F5}3)2], 34, respectively, which are examples of uranyl macrocyclic borane adducts. Reaction of complex 31 with an excess of PMe3 results in the formation of the THF-free uranyl macrocyclic complex [UO2(H2Loct)], 35.

Uranium (U) contamination can be introduced to the environment as a result of mining and manufacturing activities related to nuclear power, detonation of U-containing munitions (DoD), or nuclear weapons production/processing (DOE facilities). In oxidizing environments such as surface soils, U predominantly exists as U(VI), which is highly water soluble and very mobile in soils. U(VI) compounds typically contain the UO22+ group (uranyl compounds). The uniquely structured and long-lived green luminescence (fluorescence) of the uranyl ion (under UV radiation) has been studied and remained a strong topic of interest for two centuries. The presented research is distinct in its objective of improving capabilities for remotely sensing U contamination by understanding what environmental conditions are ideal for detection and need to be taken into consideration. Specific focuses include: 1) the accumulation and fluorescence enhancement of uranyl compounds at soil surfaces using distributed silica gel, and 2) environmental factors capable of influencing the luminescence response, directly or indirectly. In a complex environmental system, matrix effects co-exist from key soil parameters including moisture content (affected by evaporation, temperature and humidity), soil texture, pH, CEC, organic matter and iron content. Chapter 1 is a review of pertinent background information and provides justification for the selected key environmental parameters. Chapter 2 presents empirical investigations related to the fluorescence detection and characterization of uranyl compounds in soil and aqueous samples. An integrative experimental design was employed, testing different soils, generating steady-state fluorescence spectra, and building a comprehensive dataset which was then utilized to simultaneously test three hypotheses: The fluorescence detection of uranyl compounds is dependent upon 1) the key soil parameters, 2) the concentration of U contamination, and 3) time of analysis, specifically following the application of silica gel enhancing material. A variety of statistical approaches were employed, including the development of multiple regression models for predicting both intensity and band structure responses. These statistical models validated the first two listed hypotheses, while the third hypothesis was not supported by this dataset. The combination of inadequate moisture levels and reaction times (≤ 24 hrs) greatly limited the detection of varying levels of U, depending on the soil.

Thesis (Ph.D.)--Boston University / Due to the necessity of recovering uranium from reactor fuels, a number of separation methods have been investigated in recent years. Of these, the method of solvent extraction has proved to be a practical one. Long chain symmetrical phosphine oxides have been shown to extract uranium and a number of other metals under different conditions. It was the object of the present investigation to establish the nature of the species resulting from uranyl nitrate-R3Po (R =alkyl group) interaction. The two phosphine oxides selected for the study were: (i) Tri-n-octylphosphine oxide (TOPO) and (ii) Tris(2-ethylhexyl)phosphine oxide (TEHPO). An attempt was made to obtain pure TEHPO. Though the attempt has not met with complete success, yet significant conclusions concerning the stoichiometry and relative stability of the uranyl nitrate-TEHPO complex could be drawn. [TRUNCATED]

Yes / Uranyl complexes of a large, compartmental N8-macrocycle adopt a rigid, “Pacman” geometry that stabilizes the UV oxidation state and promotes chemistry at a single uranyl oxo-group. We present here new and straightforward routes to singly reduced and oxo-silylated uranyl Pacman complexes and propose mechanisms that account for the product formation, and the byproduct distributions that are formed using alternative reagents. Uranyl(VI) Pacman complexes in which one oxo-group is functionalized by a single metal cation are activated toward single-electron reduction. As such, the addition of a second equivalent of a Lewis acidic metal complex such as MgN″2 (N″ = N(SiMe3)2) forms a uranyl(V) complex in which both oxo-groups are Mg functionalized as a result of Mg−N bond homolysis. In contrast, reactions with the less Lewis acidic complex [Zn(N″)Cl] favor the formation of weaker U−O−Zn dative interactions, leading to reductive silylation of the uranyl oxo-group in preference to metalation. Spectroscopic, crystallographic, and computational analysis of these reactions and of oxo-metalated products isolated by other routes have allowed us to propose mechanisms that account for pathways to metalation or silylation of the exo-oxogroup.

No description available.

Crystals of the title compound are monoclinic with a= 8.314 (5), b= 22.723 (9), c= 12.589 (6) A, /3= 123.0 (2t, Z=4, space group P2dc. The structure was determined by Patterson and Fourier methods and refined by full-matrix least squares to a final R of 0.030 for 2043 independent reflexions. The U atom has pentagonal bipyramidal coordination and the N-methylacetylacetoneamine is bonded to U via O. There are two intramolecular N-H. . .0 hydrogen bonds which govern the geometry of the adduct molecule.

This thesis describes the reductive functionalisation of the uranyl(VI) dication by metalation of the uranyl oxo-groups (O=UVI=O), using reductants from Group I, Group II, Group IV, Group XII and Group XIII as well as from the lanthanide and actinide series of the periodic table. Chapter 1 introduces uranium and nuclear waste, and gives an introduction into uranium(V) chemistry. It further compares the chemistry of uranyl(V) to neptunyl(V), with a specific focus on solid state interactions. The chemistry of the Pacman calixpyrroles is briefly introduced. These macrocyclic ligands form the basis for the synthesis of uranyl Pacman, which represents the major uranyl complex investigated in this thesis. Chapter 2 describes the reductive and catalytic uranyl oxo-group metalation using Group XIII and Group I reagents. It presents the reductive uranyl alumination using di-(iso-butyl)-aluminium hydride and Tebbe’s reagent to form the first Al(III)- uranyl(V) oxo complexes (AlIII-O-UV=O). The chapter shows how the transmetalation of these aluminated uranyl(V) complexes with alkali metal hydrides and alkyls leads to the formation of mono-metalated alkali metal uranyl(V) complexes (MI-O-UV=O). The combination of these two reactions is developed into a catalytic synthesis of the latter. The use of elemental alkali metals is described as another pathway of accessing alkali metal uranyl(V) complexes, carried out in collaboration with Dr. Rianne M. Lord. Chapter 3 describes the synthesis of the first Group IV uranyl(V) complexes, using low-valent titanium and zirconium starting materials. The chapter includes magnetic measurements on the first Ti(III)-uranyl(V) complex and a comparison of computational results regarding a selection of uranyl(V) complexes from this thesis. The magnetic measurements were carried out by Dr. Alessandro Prescimone, University of Edinburgh, and analysed by Dr. Nicola Magnani, Institute for Transuranium Elements, Karlsruhe, Germany. Theoretical calculations were carried out by Xiaobin Zhang and Prof. Dr. Georg Schreckenbach, University of Manitoba, Canada. The chapter further describes the reductive metalation of uranyl using elemental Mg, Ca and Zn and their respective metal halides. Chapter 4 describes the uranyl functionalisation using f-elements and their complexes. It describes the attempted mono-metalation using lanthanides and the formation of a Sm(III)-bis(uranyl(V)) complex. It further describes the uranyl reduction using actinides and the synthesis of the first U(IV)-uranyl(V) complex. The chapter further describes the first Np(IV)-uranyl(V) complex and the attempted synthesis of a Pu(IV)-uranyl(V) complex. These syntheses were performed in collaboration with Michał S. Dutkiewicz at the Institute for Transuranium Elements (ITU) in Karlsruhe, Germany. This work was carried out with the help of Dr. Christos Apostolidis and Dr. Olaf Walter and supervised by Prof. Dr Roberto Caciuffo. Chapter 5 describes the reductive uranyl functionalisation in a redox-active dipyrromethene ligand, collaboratively carried out with James R. Pankhurst and Lucy N. Platts. The synthetic work and analyses were performed jointly with Lucy N. Platts (master student under the supervision of the author); UV-vis spectra and cyclic voltammograms were recorded by James R. Pankhurst and Lucy N. Platts. The chapter presents the synthesis of a new uranyl(VI) complex and its two-electron reduction to uranium(IV) using a titanium(III) reductant. Additionally the chapter describes the reductive uranyl silylation in a dipyrromethane complex of which the ligand was designed by Dr. Daniel Betz. Section 6 describes the synthetic procedures. Section 7 gives references to the work of others. Section 8 shows the publication related to this thesis. Section 9 is a table of the complexes described in this thesis.

Les composés à base de lanthanide jouent un rôle important pour différentes propriétés (optiques, magnétiques ... ) mais aussi dans le domaine des matériaux du nucléaire (matrices de conditionnement des actinides, produits de fission, simulants des actinides (III). ). La première partie de ce travail est consacrée à l'étude des vanadates d'uranyle et de lanthanide. Par voie solide, un seul composé a pu être obtenu Sa structure est bâtie sur des feuillets simples uranophane ∞ ²[(UO2)(VO4)]- et des feuillets doubles ∞²[La(UO2)(V2O7)2]+ particulièrement originaux se déduisant des feuillets uranophane par remplacement d'un atome duranium sur deux par le lanthane. Par synthèse hydrothermale, les phases TR(VUO6)3•xH2O ont été obtenues. leur structure est basée sur l'empilement de couches de type carnotite ∞²[(UO2)2V2O8]²- liées entre elles par la terre rare. La seconde partie est dédiée à l'étude de systèmes amine - lanthanide - oxalate. Les composés obtenus par croissance cristalline dans un gel appartiennent à une série d'oxalates de structure bi-dimensionnelle appelée "série quadratique" dont les feuillets se composent de polyèdres LnO8(H2O) reliés par des ions oxalate et formant des cycles "carrés". Par synthèse hydrcthermale, d'autres composés de même formule générale, (CnH2n(NH3)2)0,5[Ln(H2O)(C2O4)2]•xH2O mais présentant des arrangements structuraux différents. bi-dimensionnel et tri-dimensionnel, ont été obtenus. Enfin. l'utilisation de monoammes toujours en conditions hydrothermales a permis l'obtention d'oxalates et d'hydroxy-oxalates de néodyme originaux ne contenant pas d'amine. / Lanthanide-based compounds exhibit interestmg physical properties (optical, magnetic .. ) but also play an important role in the field of nuclear industry as matrices for actinides, fission products or actinide (III) surrogates for example.The first part of this work is devoted to the study of uranyl-vanadate and lanthanide compounds 8y solid-state reaction, the new compound La(UO2l2(VO4)(V2O7) cou Id be obtained Its structure is based on the association of uranophane sheets ∞ ²[(UO2)(VO4)]- and of double layers ∞²[La(UO2)(V2O7)2]+, in which half of the uranium atoms are replaced by lanthanum atoms. The phase TR(VUO6)3•xH2O were obtained by using hydrothermal synthesis Their structure IS based on the stacking of carnotite type layers ∞²[(UO2)2V2O8]²- linked together by the rare earth elementThe second part concerns the study of various amine-Ianthanide-oxalate systems. The diamines contained lanthanide-oxalates which were obtained by growing crystals in gel. belong to the series of oxalates named "quadratic" Their two-dimensional structure is formed by sheets in whlch the LnO8(H2O) polyhedra linked by oxalate ions form "square" rings. By hydrothermal synthesis, two compounds exhibiting the sa me general formula (CnH2n(NH3)2)0,5[Ln(H2O)(C2O4)2]•xH2O but having different structural arrangements, two-dimensional and three-dimenslonal. were obtained. Finally. using monoamines instead of diamines under hydrothermal conditions. lead to the synthesis of new neodymium oxalates and hydroxy-oxalates with no amine contamed.

Chapter one introduces uranium oxo chemistry with a focus on the structure, oxogroup reactivity and single electron reduction of the uranyl(VI) dication. In this context, the previous work in our group on the use of Schiff-base Pacman complexes for the reductive functionalisation of uranyl will be discussed. Chapter two details the synthesis of binuclear uranium(V) oxo complexes [(RMe2SiOUO)2(L)] (R = Me, Ph) by oxo group rearrangement and reductive silylation of uranyl(VI) silylamido precursors. The electronic structure and magnetic behaviour of the complexes are presented as well as insights into the mechanism of formation and stability. Chapter three describes the reduction and desilylation reactions of [(Me3SiOUO)2(L)]. It begins with the one- and two-electron reductions of [(Me3SiOUO)2(L)] and continues with the reactivity of the resultant mixed-valence complex K[(Me3SiOUO)2(L)]. The reactivity of the UIVUIV complex K2[(Me3SiOUO)2(L)] with water is detailed and the products, K[(OUVO)(OUIVOSiMe3)(L)] and a U12O24L6 supramolecular wheel are reported. The oxidation of K2[(Me3SiOUO)2(L)] with pyridine-N-oxide is demonstrated as a route to metalated K2[(OUO)2(L)] complexes, and the synthesis of Li2[(OUO)2(L)] and the mixed lithiated/silylated complex Li[(OUO)(OUOSiMe3)(L)] are presented as direct routes to Mx[(OUO)2(L)] complexes. Chapter four discusses the reactivity of M2[(OUO)2(L)] (M = K, Li) towards oxidation and oxo-functionalisation. The oxo- and peroxo-bridged binuclear uranyl(VI) complexes K2[(UO2)2(μ-X)(L)] (X = O2–, O2 2–) are reported from the reaction of K2[(OUO)2(L)] with different oxo-oxidising agents and the new, Group 14-functionalised oxo complexes [(ROUO)2(L)] (R = stannyl or alkyl group) are described showing similar structures, bonding and stabilities to the silylated complexes. Chapter five describes the uranyl(VI) complexes of other polypyrrolic ligands. The uranyl(VI) chemistry of the anthracenyl- and fluorenyl-substituted Pacman ligands LF and LA is demonstrated as a means of using macrocyclic control to govern the nature of the complexes formed. Uranyl(VI) complexes of the polypyrrolic, tripodal ligand H3LT are shown to form either molecular species or supramolecular gels depending on the solvent used. Chapter six concludes the work presented in this Thesis. Chapter seven outlines all experimental details.

Made available in DSpace on 2014-10-09T12:36:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:33Z (GMT). No. of bitstreams: 1 04249.pdf: 5660518 bytes, checksum: 38b06d640af5aad7bcd37848e79ce9dc (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP